refactor(audio): move biome BGM loop points to assets submodule

[DayKev]

What are the changes the user will see?

N/A

Why am I making these changes?

Requested. Should make modifying biome BGM easier in the future.

What are the changes from a developer perspective?

Biome BGM loop points moved out of the biome definitions and into a JSON file in the assets submodule.

Checklist

• The PR content is correctly formatted:
  • I'm using beta as my base branch
  • The current branch is not named beta, main or the name of another long-lived feature branch
  • I have provided a clear explanation of the changes within the PR description
  • The PR title matches the Conventional Commits format (as described in CONTRIBUTING.md)
• The PR is self-contained and cannot be split into smaller PRs
• There is no overlap with another open PR
• The PR has been confirmed to work correctly:
  • I have tested the changes manually

Does this require any additions or changes to in-game assets? If so:

• I have created an associated PR on the assets repository
  • If so, include a link to the PR here: refactor(audio): move biome BGM loop points to assets submodule pokerogue-assets#68

[github-actions]

This pull request is blocked until the associated assets PR is merged.
To unblock and update the assets submodule, add the Update Assets label.

Assets updated, unblocking PR.